Athens: Three executives of a defunct Cypriot airline and a British engineer were each sentenced in absentia to 10 years in prison on Friday for their role in Greece's worst air crash that killed 121 people, court officials said.

The Helios Airways Boeing 737-300 crashed into a mountain near Athens in 2005 after its oxygen supply failed and the pilots and most of the passengers fell unconscious.

An Athens court found the defendants guilty of manslaughter and negligence charges, officials told. Lawyers for the four - Helios's former chief executive officer, its chief of flight operations, the firm's Bulgarian head pilot as well as a British engineer who had inspected the plane before it took off - said they had appealed against the decision.

The ruling came four months after a Cypriot court acquitted the three executives during a separate hearing over the accident. Investigators have said the failure to switch a valve affected the oxygen supply to the aircraft shortly after the plane took off from Cyprus's Larnaca airport .

The aircraft flew on autopilot in Greek air space for two hours before it ran out of fuel and smashed into a hillside. Greek air force pilots who trailed the aircraft saw a lone man at the controls of the plane, apparently trying in vain to avert the disaster. (Agencies)